by Dr. Emil Katz
(Tel Aviv , Israel)
Question from Dr. Emil Katz:
I am 67 years old and exercise intensively every day. My morning glucose level has been 120–135 mg/dL for the last 10 years.
In the afternoon, 3–4 hours after lunch, my glucose level is below 100 mg/dL.
Can my normal fasting level simply be slightly outside the statistics, meaning my personal cut-off is not 126 mg/dL but perhaps 135 mg/dL?
A fasting glucose of 120–135 mg/dL should not be dismissed as “normal for you.” Fasting glucose from 100–125 mg/dL is usually in the prediabetes range, while 126 mg/dL or higher on repeat testing meets the diabetes range.
It is possible to have higher morning readings and normal afternoon readings. Common reasons include the dawn phenomenon, overnight liver glucose release, insulin resistance, dinner composition, sleep quality, stress, or timing of exercise.
The best next step is to review HbA1c, repeat fasting glucose, and possibly an oral glucose tolerance test or CGM pattern with your doctor.
Answer by Dr. Albana Greca, MD, MMedSc
Hi Dr. Katz,
Your question is thoughtful. Individual variation exists in biology, but diagnostic glucose thresholds are not meant to describe what feels normal for one person. They are used because risk of diabetes-related complications rises as glucose exposure increases.
Not necessarily. Many people have higher fasting glucose in the morning but lower glucose later in the day. This can happen because early-morning hormones tell the liver to release glucose. In people with insulin resistance or reduced insulin response, that glucose rise may not be fully controlled.
This is often called the dawn phenomenon. ADA also describes morning highs as commonly related to the dawn phenomenon or waning insulin effect.
I would be careful with that interpretation. A fasting value of 135 mg/dL is above the standard diagnostic threshold for diabetes if confirmed on repeat testing. A personal “normal” should not replace validated diagnostic ranges.
That said, one fasting glucose number should be interpreted together with HbA1c, repeat fasting tests, after-meal readings, symptoms, medication use, kidney function, anemia status, and overall cardiovascular risk.
You may compare values here: normal fasting blood sugar levels.
Your afternoon glucose below 100 mg/dL is reassuring, but it does not cancel out repeated high fasting readings. Intensive daily exercise can improve muscle glucose uptake and may explain lower later-day values.
The pattern may suggest isolated fasting hyperglycemia, dawn phenomenon, hepatic glucose output, or early insulin resistance. A CGM can be useful because it shows the overnight pattern, not only a single morning value.
You may also use this page: HbA1c to average glucose calculator.
Repeated fasting readings of 126 mg/dL or higher should be reviewed with a clinician. Do not ignore them because afternoon readings are normal. Diagnosis and treatment decisions should be based on confirmed laboratory results and overall risk.
Your lower afternoon glucose is encouraging, but fasting readings of 120–135 mg/dL deserve follow-up. I would not redefine 135 mg/dL as normal without checking HbA1c, repeat fasting glucose, and possibly CGM or oral glucose tolerance testing.
Educational safety note: This answer is for general diabetes education only. It does not replace personal medical advice, diagnosis, or treatment. Please discuss repeated fasting glucose above target with your healthcare provider.
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